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What size pipe for hookup to main line coming into house

I am going to install my own sprinkler system. My main water line is 1 1/4 inches. Now i have to tee off to the valves and was told to go one size bigger to 1 1/2inches is this correct. Seems kinda big.

We really need more information to help with this question. How many gallons per minute are you going to design
each zone to operate at. 8, 12, 18, 25,G.P.M. What you need to answer this questions is how big of an area are you
going to irrigate? What is your water source? How far are you going to irrigate from the water source. This will help
Determine how big your mainline will be.

We really need more information to help with this question. How many gallons per minute are you going to design
each zone to operate at. 8, 12, 18, 25,G.P.M. What you need to answer this questions is how big of an area are you
going to irrigate? What is your water source? How far are you going to irrigate from the water source. This will help
Determine how big your mainline will be.

For example, if you only need 5gpm, then 1-1/4 is already more than big enough and going up to 1-1/2 is just a waste of $$$ on buying larger pipe. From a cost perspective, you want to TRY to use just 1" pipe because it's so common that even if you could reduce to 3/4", the cost difference between 3/4" and 1" isn't that great. But once you get above 1", prices jump pretty severly. But if you need 20gpm at a point 200' away, then yea, you might need to consider upsizing the pipe.